One of the major problems facing the wineries in the Northeastern United States is the high-acid wines. The climatic conditions as well as the short growing season results in a high total acidity. It is not uncommon for a wine to have a total acidity of 1.2%. Malic acid is the major contributor to this problem. The high malic concentration as well as the lower pH can result in a very high malic acid content in the wines, since 55% to 70% of the total malate is present in the acid form. The other major wine acid, tartaric, does not pose a problem in the acidity of the wine, since its concentration is drastically reduced during the fermentation due to the deposition of potassium bitartrate.
There have been many attempts to lower the acidity of the Eastern wines using physical, biological, and chemical methods:
A. Physical Methods:
1. Amelioration with water to dilute the acidity. PA1 2. Blending with low-acid wines. PA1 3. Covering the acid taste with the addition of sugar. PA1 1. Malo-lactic fermentation. PA1 2. Double fermentation with Schizosaccharomyces pombe followed by Saccharomyces cerevisiae. PA1 1. Double salt precipitation PA1 2. Neutralization with K.sub.2 CO.sub.3 PA1 3. Neutralization and precipitation with CaCO.sub.3.
B. Biological Methods:
C. Chemical Methods:
All three methods have considerable disadvantages since in many cases the end results may give rise to other problems. By using the physical methods outlined the acid is diluted to reduce acidity in the case of amelioration or blending with low-acid wines while the acid flavor is masked in the case of the addition of sugar. As to the biological methods, results are not always predictable. Ideal conditions have to exist for the malo-lactic fermentation. pH values of these wines are usually between 3.1 to 3.3. This would mean that between 13 and 19 parts per million free SO.sub.2 in the wine would retard the growth of the malo-lactic organism. The Schizosaccharomyces pombe would impart an off-flavor to the wine. Employing a chemical method involves the addition of various chemicals which can cause stability as well as flavor problems for the product. In the case of the CaCO.sub.3 and the double salt methods a stability problem will result since the calcium concentration is increased, whereas with the use of potassium carbonate, a stability problem as well as a flavor problem can result if the acidity is reduced to any great extent. A maximum reduction between 0.15% to 0.2% total acid, calculated as tartaric acid, can be done with the potassium carbonate without any adverse flavor effects; much over this amount, a metallic character will result in the wine.
Ion exchange has been used in the wine industry for many years. Stabilization of wines using a cation exchange to replace the potassium in wine with sodium has been used by the industry throughout the world. Further, it has been employed in the case of low-acid wines to increase the acidity of the wine by using a cation exchange of the potassium with hydrogen ion. The thought that the acidity of wines could be reduced without the addition of any substance using ion exchange could be an ideal method of reducing the acidity. The initial thought was to employ an anion exchange to remove the acids; it was observed that strongly basic anion exchange resins, which are primarily quaternary ammonium type structures, imparted a "fish-like" flavor to the wines probably due to the liberation of trimethylamine. The anion exchange using the weakly basic resin in the salt form caused a "soap-like" or salty character to the wine.
It is also known in the art that total acidity and particularily volatile acidity in substandard wines (greater than 0.14 grams per 100 ml calculated as acetic acid) can be reduced by the use of a cation exchange column followed by an anion exchange employing a porous resin (see U.S. Pat. No. 2,682,468).
It is also known in the art that flavor, aroma and color of fortified wines can be improved by first passage through a porous anion exchange resin in the hydroxyl form followed by a porous cation exchange resin employed in the H.sup.30 form, however, this form of treatment results in a significant decrease in pH and in many cases increases total acidity (see U.S. Pat. No. 3,437,491).